Light mimics magnetic response in photonic crystal experiments
by Clarence Oxford
Los Angeles CA (SPX) Apr 26, 2024

Researchers at Penn State have achieved a significant milestone by making light "feel" a magnetic field within a photonic crystal composed of silicon and glass. The light within the crystal behaves similarly to electrons, spinning in circles and forming discrete energy bands, a phenomenon typically associated with electrons in magnetic fields. This discovery opens up potential new methods for enhancing the interaction between light and matter, potentially benefiting photonic technologies like compact lasers.

The experiments, based on a theoretical prediction by Penn State's Professor of Physics Mikael Rechtsman, graduate student Jonathan Guglielmon, and Columbia University mathematician Michael Weinstein, were detailed in a paper released in Nature Photonics. This paper coincides with a parallel study by researchers in the Netherlands, led by Ewold Verhagen, which observed similar phenomena.

"For charged particles like electrons, there is a lot of interesting physics that results from their interactions with magnetic fields," said Rechtsman, the leader of the research team. "Because of this, there has been an interest in emulating this physics for photons, which are not charged and so do not respond to magnetic fields."

The Penn State team crafted tiny slabs of silicon into a honeycomb lattice with nanoscale triangular holes, creating a photonic crystal only 1/1000th the thickness of human hair. By shining laser light into this crystal and manipulating the lattice structure to simulate a magnetic field through "strain," the team was able to make light move in circular orbits and exhibit energy bands similar to Landau levels in electrons.

The light in the unstrained lattice spreads evenly, but in the strained version, it moves in circles and forms discrete energy bands. "The curved nature of the bands is known as dispersion," Rechtsman said. "To try to mitigate the dispersion, we added an additional strain to the pattern. This added strain, which acts as a pseudo-electric potential, counteracts the dispersion, giving us flat-band Landau levels just like those from electrons."

This research was supported by Penn State X-ray astronomers Randall McEntaffer and Fabien Grise, and involved graduate students Maria Barsukova and Zeyu Zhang, under the guidance of another student, Sachin Vaidya. The team also collaborated with Li He and Bo Zhen from the University of Pennsylvania.

Research Report:Direct observation of Landau levels in silicon photonic crystals

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